This invention relates to a new use of stainless steel. Stainless steel hypodermic needles are used in raising livestock to be processed in meat packing plants. The needles break leaving metal in processed meat. Although metal detectors are employed in most meat packing plants, currently they don""t detect stainless steel needles in meat.
Needles, which have broken off in livestock, are a problem in processed meat. Although disposable, in the field they are used repeatedly until they snap or break off in livestock (pigs and cattle). The needle has a stainless steel cannula fixed in a hub. The cannula breaks away from the hub or the cannula itself breaks, and remains unrecovered in the animal. Hubs are generally plastic (often polypropylene), aluminum, or chromium coated brass. Broken needles are more common in pork than beef because of the sheer volume of pigs processed each year. Needles will be present in processed meat from all livestock subject to injection. The current disposable needles used in the raising of livestock are usually made of 304 stainless steel, an austenitic alloy typically about 18 to 20% chromium and 8 to 12% nickel. It is not magnetic and needles made of it are not detectable by metal detectors currently used in meat plants, nor are other disposable hypodermic needles made of non-magnetic metals and alloys. One hundred million disposable hypodermic needles are used yearly. The current usage of disposable needles in the raising of livestock causes them to break. These undetectable needles end up in processed meat and pass through packing plants, which are sold to consumers, domestically and internationally. Many meat packing plants in North America use metal detectors in an attempt to detect and remove disposable hypodermic needles from processed meat. Despite this practice few, if any, disposable needles are detected and removed. For all practical purposes disposable hypodermic needles of austenitic 304 stainless steel and other non-magnetic metals and alloys are not detectable.
The problem is as at least as old as disposable hypodermic needles, and the meat packing industry is well aware of it. The problem has not been addressed by the needle manufacturers, who are also aware of the problem. The suggestion sometimes made that the stainless steel disposable needles should not be used in livestock raising, or at any rate not repeatedly used, is fanciful and not at all practical.
Although this suggestion is obviously ridiculous it is the sole suggestion to emerge from an in depth study at the Iowa State University, Ames (Hoff et. al., American Journal of Veterinary Research, 60, No.3, 292-298, 1999) which concluded that stainless steel needles and their hubs were sufficiently resilient to avoid breakage in single use. The contributory factor of breakage is that the animal moves when injected deforming the needle. The prime cause of breakage is that the deformed needle is straightened by hand and reused. The needle when straightened is much more likely to break off in the animal, and the chance increases with repeated straightening. While the manufacturers place product notices on needle packaging specifying xe2x80x9csingle use onlyxe2x80x9d, this is not followed in practice. The Iowa study also recommended xe2x80x9csingle use only.xe2x80x9d
There is increasing worry about disposable needles in the processed meat industry especially since complaints and presumably incidence are increasing. Export contracts are especially sensitive to the discovery of needles in meat. Two surveys were carried out in 1999 in Canada by the Canadian Cattlemen, a trade publication; one of veterinarians, one of processors, purveyors and retailers. The veterinarians (25% of whom had experienced broken needles) recommended use of proper animal restraints (50%, but difficult in practice), restricted reuse of the needle 5 to 20 times (41%), and discarding damaged needles (28%). Of the producers 41% had from 1 to 12 complaints about needles in the average year, 30% had metal detectors, and 31% used metal detectors (14% supplemented by visual inspection), about 14% passed all products through a metal detector, and another 14% passed some products through a metal detector. About 73% had high confidence in metal detection in trim (not whole muscle), 18% medium and 9% low. The surveys as summarized (Donkersgoed, Canadian Cattlemen, January 2000, p. 28) stated that the processors had little confidence in the ability of metal detectors to detect metal in large cuts of meat. As noted above, austenitic stainless steel is non-magnetic and one of the hardest metals to detect using a metal detector.
There are four groups involved, the needle manufacturers, veterinarians, producers, meat packers. Neither the packer nor the producer can rely on the other to detect needles in meat. In practice the packer is liable, because it is difficult if not impossible to identify the producer. Although some meat packing plants use metal detectors these are rarely successful in detecting needles.
There is therefore a need for detectable disposable needles. Current common needles come in several sizes especially 20 gaugexc3x97xc2xd inch, 18 gaugexc3x971 inch, 18 gaugexc3x971xc2xd inch, 16 gaugexc3x971 inch, 16 gaugexc3x971xc2xd inch, 14 gaugexc3x971 inch, 14 gaugexc3x971xc2xd inch, with larger needles used for larger animals and smaller needles for smaller animals. The primary need is to detect the smallest needles when broken off (20 gaugexc3x97xc2xd inch), and preferably smaller broken portions of such needles.
Applicant is not aware of any prior art.
It is a principal object of the invention to provide hypodermic needles detectable in meat by metal detectors currently used in meat packing plants. It is a subsidiary object of the invention to provide hypodermic needles detectable in meat as broken portions by metal detectors currently used in meat packing plants.
The invention in its broadest aspect is directed to a magnetic stainless steel hypodermic needle detectable in meat by metal detectors. The magnetic stainless steel is preferably selected from the group of ferritic and martensitic stainless steels. The stainless steel may be ferritic, preferably 430 stainless steel, or it may be martensitic, preferably 420 stainless steel. The needle is preferably of length from xc2xd to 1xc2xd inches long and gauge from 14 to 20. The needle may be of length xc2xd inch and gauge 20, of length 1 inch and gauge 18, of length 1xc2xd inch and gauge 18, of length 1 inch and gauge 16, of length 1xc2xd inch and gauge 16, of length 1 inch and gauge 14, of length 1xc2xd inch and gauge 14.
In another aspect the invention is directed to the novel use of magnetic stainless steel in disposable hypodermic needles, detectable in meat by metal detectors. The magnetic stainless steel is preferably selected from the group consisting of ferritic and martensitic stainless steel. More preferably the stainless steel is martensitic stainless steel, conveniently 420 stainless steel. Also more preferably the stainless steel is ferritic stainless steel, conveniently 430 stainless steel.
In another aspect the invention is directed to the manufacture of disposable hypodermic needles detectable in meat by metal detectors from magnetic stainless steel. The magnetic stainless steel is preferably selected from the group consisting of ferritic and martensitic stainless steel. More preferably the stainless steel is martensitic stainless steel, conveniently 420 stainless steel. Also more preferably the stainless steel is ferritic stainless steel, conveniently 430 stainless steel. The preferred method of manufacture is cold drawing of tubular stock, which typically requires several iterations.